8/11/2019: After the initial heady successes I decided to ‘formalise’ things somewhat. This entailed making the whole setup more repeatable and remove the need for my hands to be anywhere near the setup for firing. The initial result was an Arduino Uno controlling the charging circuit via a solid state relay and of course the firing of the SCR. Control was by a couple of momentary switches into the Arduino. I also changed the power supply to a 60v transformer that I had laying around.

There were some interesting moments in the processes above. A couple of times the projectile fired out the wrong end of the barrel but this was entirely my fault for doing silly things. The second oops was when the SCR didn’t shut down a few times making the current limiting resistor extremely hot – fried egg hot. It also fired when I shut down the transformer charging the capacitors, interesting. Never mind, getting there now.

After a couple of oops moments I have now got it all working. I’m now working on more information being available to me at a glance. This is mainly around knowing voltages at all points of the system and possibly the temperature of the charging current limiting charge resistor. I managed to get this very hot at one of point when the SCR didn’t shut off when expected.